Motion picture encoding device and motion picture decoding device

ABSTRACT

When a prediction is made between fields with different parity, the predicative efficiency of a chrominance vector is improved by adaptively switching the generation of a chrominance motion vector depending on a encoding/decoding field parity (top/bottom) and a reference field parity (top/bottom), and the coding efficiency is improved accordingly.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention The present invention relates to amotion picture encoding device and a motion picture decoding device,which have an inter-field prediction mode.

[0002] 2. Description of the related Art

[0003] Generally, motion picture data is large in size Therefore, whenmotion picture data is transmitted from a transmitting device to areceiving device or when it is stored in a storage device, highlyefficient encoding is applied to motion picture data. In this case,“highly efficient encoding” is an encoding process of converting aspecific data string into another data string, and compressing theamount of data.

[0004] There are two types of motion picture data: one is mainlycomposed of only frames and the other is composed of fields. A prior artfor compressing a field image is mainly described below.

[0005] As the highly efficient encoding method of motion picture data, aframe/field prediction encoding is known.

[0006]FIG. 1 shows a block diagram of the configuration of theframe/field predictive encoding device.

[0007] This encoding method utilizes the fact that a plurality ofsegments of motion picture data has high correlation in a time directionwith each other. The operation shown in FIG. 1 is roughly describedbelow. A subtracter 39 generates a differential image between aninputted original image and a predicted image, and an orthogonaltransform unit 31, a quantization unit 32 and a coefficient entropyencoding unit 40 encode the differential image. An inverse quantizationunit 33 and an inverse orthogonal transform unit 34 reproduce thedifferential image from the output of the quantization unit 32. Then, adecoded image generation unit 35 decodes the encoded image using thereproduced differential image reproduced by the decoded image generationunit 35 and the predicted image used at the time of encoding. A decodedimage storage unit 36 stores the reproduced image. Then, motion vectorcalculation unit 37 calculates a motion vector between the reproducedimage and a subsequent input image, and a predicted image generationunit 38 generates a predicted image using the motion vector. Thegenerated motion vector is encoded by a vector entropy encoding unit 41and is outputted through a MUX 42 together with the encoded coefficientdata encoded by the coefficient entropy encoding unit 40. In otherwords, since in motion picture data, there is generally high similaritybetween frame/field data at a specific time and frame/field data at asubsequent time, the inter-frame/field predictive encoding methodutilizes such a property. For example, in a data transmission systemadopting the inter-frame/field predictive encoding method, atransmitting device generates motion vector data indicating displacementfrom previous frame/field image to a target frame/field image, anddifferential data between a predicted image in the target frame/fieldwhich is generated from the previous frame/field image using its motionvector data and a real image in the target frame/field, and transmitsthe motion vector data and the differential data to a receiving device.The receiving device reproduces the image in the target frame/field fromthe received motion vector data and differential data.

[0008] So far, the summary of the frame/field predictive encoding hasbeen described with reference to FIG. 1. Next, frame predictive encodingand field predictive encoding are described below.

[0009]FIGS. 2 and 3 show a format used to encode a field image that iscommonly used in ISO/IEC MPEG-2/MPEG-4 (hereinafter called “MPEG-2” and“MPEG-4”, respectively) and the final committee draft of ITU-TH.264/ISO/IEC MPEG-4 Part 10 (Advanced video coding (AVC)) (“Joint FinalCommittee Draft (JFCD) of Joint Video Specification (ITU-TREC,H.26411SO/IEC 14496-10AVC)”, JVT-D157, or ISO/IEC JTC1/SO29/WG11MPEG02/N492, July 2002, Klagenfurt, AT)(hereinafter called “AVC FCD”),which ITU-T and ISO/IEC jointly were standardizing as of August 2002.Specifically, each frame is composed of two fields: a top field and abottom field. FIG. 2 shows the respective positions of a luminancepixels and a chrominance pixels, and a field to which each pixelbelongs. As shown in FIG. 2, odd number-ordered luminance lines, such asa first luminance line (50 a), a third luminance line (50 b), a fifthluminance line (50 c), a seventh luminance line (50 d), etc., belong tothe top field, and even number-ordered lines, such as a second luminanceline (51 a), a fourth luminance line (51 b), a sixth luminance line (51c), a eighth luminance line (51 d), etc., belong to the bottom field.Similarly, odd number-ordered chrominance lines, such as a firstchrominance line (52 a), a third chrominance line (52 b), etc., belongto the top field, and even number-ordered chrominance line, such as asecond chrominance (53 a), a fourth chrominance line, etc., belong tothe bottom field.

[0010] Each of the top and bottom fields indicates an image at adifferent time. Next, the time/spatial disposition of the top and bottomfields is described with reference to FIG. 3.

[0011] In FIG. 3 and after, the technology of the present inventionrelates to the vertical component of a motion vector. Therefore, in thisspecification, horizontal pixel components are not shown, and all thehorizontal components of the motion vector are assumed to be 0 forconvenience sake. However, in order to show conventional problems andthe effects of the present invention, the positional relation betweenluminance and chrominance in each field is accurately shown.

[0012] In FIG. 3, the vertical and horizontal axes represent the pixelposition of a vertical component in each field and the elapse of time,respectively. Since there is no positional change in a field of thehorizontal component of each image, in FIG. 3, its horizontal pixelcomponent is not shown nor is described.

[0013] As shown in FIG. 3, the pixel position of a chrominance componentdeviates from the pixel position in a field of a luminance component bya quarter vertical pixel. This is because relationship of pixelpositions as shown in FIG. 2 is achieved when a frame is constructedfrom both Top and Bottom fields. If it is based on a NTSC format, eachtime interval between adjacent top and bottom fields (64 a: 65 a, 65 a:64 b, etc.) is approximately {fraction (1/60)} seconds. Each timeinterval between two consecutive top fields (64 a: 64 b, etc.) orbetween two consecutive bottom field (65 a: 65 b, etc.) areapproximately {fraction (1/30)} seconds.

[0014] Next, the frame predictive encoding mode of a field image and itsfield prediction, which is adopted in MPEG-2 and AVC FCD, are described.

[0015]FIG. 4 shows a method for constructing a frame using twoconsecutive fields (adjacent top and bottom fields) in a framepredictive mode.

[0016] As shown in FIG. 4, a frame is reconstructed by twotime-consecutive fields (top and bottom fields).

[0017]FIG. 5 shows a frame predictive mode.

[0018] In FIG. 5 it is assumed that each frame, such as 84 a, 84 b, 84c, etc., is already reconstructed by two consecutive fields (top andbottom fields), as shown in FIG. 4. In this frame predictive mode, aframe to be encoded which is composed of top and bottom fields isencoded. As a reference image, one reference frame is constructed by twoconsecutive fields (top and bottom fields) stored for reference use, andis used to predict the target frame to be encoded. Then, these two frameimages are encoded according to the process flow shown in FIG. 1. In theexpression method of a motion vector of this frame predictive encodingmode, a zero vector, that is, (0,0) indicates a pixel located in thesame spatial position. Specifically, the motion vector (0,0) of aluminance pixel 82 that belongs to frame#2(84 b) indicates the pixelposition 81 of frame#1(84 a).

[0019] Next, a field predictive encoding mode is described.

[0020]FIG. 6 shows a predictive method in an inter-field predictivemode.

[0021] In a field predictive mode, an encoding target is one top field(94 a, 94 b, etc.) or bottom field (95 a, 95 b, etc.) that is inputtedas an original image. As a reference image, a top field or bottom fieldthat is stored before can be used. In this case, it is generally definedthat the fact that an original image field parity and a reference fieldparity are the same means that the original image field and thereference field both are top fields or bottom fields. For example, in aprediction 90 between fields with the same parity shown in FIG. 6, anoriginal image field (94 b) and a reference field (94 a) both are topfields. Similarly, it is generally defined that the fact that anoriginal image field parity and a reference field parity are differentmeans that one of original image and reference fields is a top field andthe other is a bottom field. For example, in a prediction 91 betweendifferent parity fields shown in FIG. 6, the original image field is abottom field (95 a) and the reference field is a top field (94 a). Then,these original image and reference fields are encoded according to theprocess flow shown in FIG. 1.

[0022] In the prior art, in both frame and field modes, a motion vectoris calculated based on a pixel position in each frame/field. Here, aconventional motion vector calculation method and a conventional pixelcorresponding method used when a motion vector is given are described.

[0023]FIG. 7 defines the coordinates of a frame/field image widely usedin MPEG-2 coding, MPEG-1 coding, AVC FCD coding, etc. White circles inFIG. 7 are pixel definition positions in target frames/fields. In thecoordinates of this frame/field image, the upper left corner isdesignated as the origin (0,0), and values 1, 2, 3, etc., aresequentially assigned to both horizontal and vertical pixel definitionpositions. Specifically, the coordinates of a pixel that are located atthe n-th horizontal position and the m-th vertical position are (n,m).Similarly, the coordinates of a position interpolated among the pixelsare also defined. Specifically, since a position 180 marked with a blackcircle in FIG. 7 is located at 1.5 pixels in the horizontal directionfrom the pixel located in the upper left corner and at 2 pixels in thevertical direction, the coordinates of the position 180 is expressed as(1.5, 2). In a field image, there are only a half of the pixels of aframe image in the vertical direction. However, even in this case, thecoordinates of a pixel are defined in the same way as in FIG. 7, basedon pixel positions located in each field.

[0024] Next, the definition of a motion vector between fields isdescribed using the coordinate system shown in FIG. 7.

[0025]FIG. 8 shows a conventional calculation method of a motion vectorbetween corresponding pixels between fields. The definition of a motionvector requires the position of a coding field and the position of areference field. A motion vector is defined between these two points.Thus, a motion vector between a coding field coordinates201(X_(s),Y_(s)) and a reference field coordinates 202(X_(d), Y_(d)) iscalculated. In the conventional calculation method of a motion vectorbetween pixels corresponding to between-fields, a motion vector iscalculated by the same method described below, regardless of whether thecoding field or reference field is a top field or a bottom field.Specifically, coding field coordinates 201(X_(s),Y_(s)) and referencefield coordinates 202 (X_(d), Y_(d)) are inputted to a motion vectorcalculation unit 200, and as a motion vector 203 between these twopoints, (X_(d)-X_(s),Y_(d)-Y_(s)) is given.

[0026]FIG. 9 shows a conventional method for calculating a pixel that ispointed by a motion vector defined between fields. In this case, it isassumed that a motion vector is calculated by the method shown in FIG.8. The calculation of reference frame/field coordinates requires acoding frame/field position and a motion vector. In the case shown inFIG. 9, it is assumed that a motion vector 211(X,Y) is given for codingfield coordinates 212(X_(s),Y_(s)), and reference field coordinates canbe calculated using both the motion vector 212(X,Y) and the coding fieldcoordinates 212 (X_(s),Y_(s)). In the conventional calculation method ofa motion vector between corresponding pixels between fields, a referencefield position is calculated by the same method described below,regardless of whether the coding field or reference field is a top fieldor a bottom field. Specifically, a motion vector 211(X,Y) and codingfield coordinates 212(X_(s),Y_(s)) are inputted to a pixel correspondingunit 210, and as reference field coordinates 213, coordinates(X_(s)+X,Y_(s)+Y) is given.

[0027] The definition of the relation between a vector and a pixelposition applies to both a luminance component and chrominancecomponent. In MPEG-1/MPEG-2/AVC FCD, which all are general motionpicture encoding methods, only the vector of a luminance component isencoded, and the vector of a chrominance component is calculated byscaling down the luminance component. Particularly, in AVC FCD, sincethe number of vertical pixels and that of horizontal pixels of achrominance component are a half of those of a luminance component,respectively, it is specified that a motion vector used to calculate thepredictive pixel of a chrominance component should be obtained byaccurately scaling down the motion vector of the luminance component toa half.

[0028]FIG. 10 shows a conventional method for calculating a chrominancemotion vector using a luminance motion vector.

[0029] Specifically, if a luminance motion vector 221 and a chrominancemotion vector 222 are (MV_x,MV_y) and (MVC_x, MVC_y), respectively, achrominance motion vector generation unit 220 can calculate achrominance motion vector 222 according to the following equation.

(MVC _(—) x, MVC _(—) y)=(MV _(—) x/2,MV _(—) y/2)  (1)

[0030] This conventional calculation method can be used regardless ofwhether a motion vector is used for predicttion between fields with thesame parity or between fields with different parity.

[0031] In AVC FCD, as the accuracy of the motion vector of a luminancecomponent, ¼ pixel accuracy can be applied. Therefore, as a result ofequation (1), as the accuracy of the motion vector of a chrominancecomponent, a vector having ⅛ pixel accuracy, that is, accuracy at thedecimal fraction, can be used.

[0032]FIG. 11 shows the calculation method of the interpolated pixel ofa chrominance component that is defined in AVC FCD.

[0033] In FIG. 11, a black circle and a white circle represent aninteger pixel and an interpolated pixel, respectively. In this case, thehorizontal coordinate of an interpolated pixel G(256) is obtained byinternally dividing each horizontal coordinate between points A(250) andC(252) at a ratio α:1−α, and the vertical coordinate can be obtained byinternally dividing each vertical coordinate between points A(250) andB(251) at β:1−β. In this case, α and β are a value between 0 and 1. Aninterpolated pixel G(256) defined by such positions can be roughlycalculated as follows using integer pixels A(250), B(251), C(252) andD(253), which are located around the interpolated pixel G(256), andusing α and β.

G=(1−α)·(1−β)·A+(1−α)·β·B+α·(1−β)·C+α·β·D  (2)

[0034] The interpolated pixel calculation method of a chrominancecomponent, using the method shown in FIG. 11 is just one example, andthere is no problem in using another calculation method.

[0035] In the case of this field encoding mode, in a prediction in whichan original image field and a reference field are different, that is,between fields with different parity, the respective zero vectors of themotion vector of a luminance component and that of a chrominancecomponent are not parallel in the definition of AVC FCD. Specifically,if a prediction is made using the motion vector of a chrominancecomponent calculated using the motion vector of a luminance componentaccording to the conventional definition, a pixel located in a positionspatially deviated from that of the luminance component is to bereferenced. This fact is described below with reference to FIG. 12. InFIG. 12, it is assumed that a top field 130, a bottom field 131 and atop field 132 continue timewise. In this case, bottom field 131 is to beencoded using top field 130. In this inter-field encoding, the verticalmotion vector in the same line of each field is defined to be zero.Therefore, if a zero vector (0,0) is assigned to a luminance pixel 133 athat belongs to the second line of bottom field 131, this pixel can bepredicted from a pixel 135 a in top field 130. Similarly, when a zerovector (0,0) is assigned to a chrominance pixel 133 a which belongs tothe first line of the bottom field 131, this pixel is predicted from thepixel 137 a which is in the first line of chrominance of the top field130. Similarly, a luminance pixel 133 b in the third line and achrominance pixel 134 b, which belong to top field 132 are predictedfrom pixels 135 b in the third line of luminance and 137 b in the secondline of chrominance in bottom field 131, respectively. Since essentiallyit is preferable that a chrominance motion vector and a luminance motionvector are parallel, chrominance pixels 134 a and 134 b should bepredicted from the positions 136 a and 136 b, respectively, if aluminance motion vector is as it is.

[0036] As described earlier, in a prediction between fields withdifferent parity, the fact that the respective zero vectors of luminanceand chrominance are not parallel is explained. In the case of AVC FCD,this fact causes the following problems for all vectors in a predictionbetween fields with different parity. FIGS. 13 and 14 show suchproblems. Problems in the case of AVC FCD are described below. In theexplanation below, a horizontal component of a motion vector is set tozero in all cases for brevity.

[0037]FIG. 13 shows a conventional problem caused if a chrominancemotion vector is conventionally calculated using a luminance motionvector when a reference field and a coding field are a bottom field anda top field, respectively. In AVC FCD, since, as is clear from equation(1), it is specified that the number of vertical and horizontal pixelsof a chrominance component are a half of those of a luminance component,a motion vector used to calculate the predictive pixel of a chrominanceshould be scaled down to a half of the motion vector of a luminancecomponent. This is regardless of whether a motion vector is used forpredicttion between frames, between fields with the same parity orbetween fields with different parity.

[0038] It is shown below that this definition causes a problem when achrominance motion vector is calculated using a luminance motion vectordefined between fields with different parity. In FIG. 13, a coding fieldtop field luminance pixel 140 in the first line has (0,1) as apredictive vector, and as a result, it points a bottom reference fieldluminance pixel position 141 in the second line as a predictive value.

[0039] In this case, a chrominance motion vector that belongs to thesame block is calculated to be (0,½), according to equation (1). If aprediction is made using motion vector (0,½) as a predictive value of acoding field top field chrominance pixel 142 in the first line, a pixelposition 143 is used as predicted value, which shifts downward by half apixel from a pixel in the first line of a bottom reference fieldchrominance component.

[0040] In this case, a luminance motion vector (0,1) and a chrominancevector (0,½) are not parallel. It is preferable to use a bottomreference field chrominance predictive pixel position 145 to which achrominance motion vector parallel to a luminance motion vector isapplied.

[0041]FIG. 14 shows a conventional problem caused if a chrominancemotion vector is calculated using a luminance motion vector when areference field and a coding field are a top field and a bottom field,respectively. As described in FIG. 13, in FIG. 14, a bottom coding fieldluminance pixel 150 in the first line has (0,1) as a predictive vector,and as a result, it points a reference top field luminance pixelposition 151 in the second line as a predictive value.

[0042] In this case, a chrominance motion vector that belongs to thesame block is calculated to be (0,½), according to equation (1). If aprediction is made using motion vector (0, ½) as a predictive value of abottom coding field chrominance pixel 152, a pixel position 153 is usedas predicted value which is shifted by half a pixel from a top referencefield chrominance pixel position 153 in the first line.

[0043] In this case, a luminance motion vector (0,1) and a chrominancevector (0,½) are not parallel. It is preferable to use a top referencefield chrominance predictive pixel position 155 to which a chrominancemotion vector parallel to a luminance motion vector is applied.

[0044] As described above, if a reference field parity and a codingfield parity are different, according to the conventional predictivemethod, a pixel located in the position of a luminance componentspatially deviated from that of the chrominance component is to bereferenced, and a predictive image, in which a pixel located in theposition of a luminance component is spatially deviated from that of thechrominance component, is generated not only for a zero vector but forall the vectors. Note that, in the above explanation, vector are said tobe parallel or not parallel by considering the case where the directionin time of a luminance motion vector and a chrominance motion vector,that is, time direction from coding field to reference field in includedin a motion vector. The same is true below.

SUMMARY OF THE INVENTION

[0045] It is an object of the present invention to provide a motionpicture encoding device and a motion picture decoding device capable ofparticularly improving predictive efficiency of a chrominance componentand improving encoding efficiency accordingly, in encoding betweendifferent field images.

[0046] The motion picture encoding device of the present invention formaking the inter-field motion compensation of a motion picture signalcomposed of a plurality of fields comprises a plurality of chrominancemotion vector generation units generating a chrominance motion vectorusing a luminance motion vector in a motion picture encoding device; anda selection unit selecting one of the chrominance motion vectorgeneration units used to generate a chrominance vector, using thereference field parity and coding field parity of a motion vector. Thechrominance motion vector generation unit selected by the selection unitgenerates the chrominance predictive vector, based on the motion vectorinformation of luminance information.

[0047] The motion picture decoding device of the present invention formaking the inter-field motion compensation of a motion picture signalcomposed of a plurality of fields comprises a plurality of chrominancemotion vector generation units generating a chrominance motion vectorfrom a luminance motion vector; and a selection unit selecting one ofthe chrominance motion vector generation units used to generate achrominance vector, using the reference field parity and coding fieldparity of a motion vector. The chrominance motion vector generation unitselected by the selection unit generates the chrominance predictivevector, based on the motion vector information of luminance information.

[0048] According to the present invention, since a chrominance motionvector which is generated by a suitable method based on parities of aencoding/decoding field and a reference field, is used, the discrepancyof the chrominance motion vector caused by the difference ofarrangement, or the way of assignment to a top and a bottom field ofluminance pixels and chrominance pixels, is resolved.

[0049] Additionally, by the present invention, a chrominance motionvector which is parallel to a luminance motion vector is obtained evenin the case of fields with different parity, and the problem of a shiftof reference pixel position between luminance components and chrominancecomponents in the conventional method, is resolved.

BRIEF DESCRIPTION OF THE DRAWINGS

[0050]FIG. 1 shows the configuration of an inter-frame predictiveencoding device;

[0051]FIG. 2 shows the respective positions of luminance and chrominancepixels and a field to which each of them belongs;

[0052]FIG. 3 shows the respective vertical time and spatial positions ofluminance and chrominance pixels in a field image;

[0053]FIG. 4 shows the relation between a field and a frame in a frameencoding mode;

[0054]FIG. 5 shows a predictive method in an inter-frame predictiveencoding mode;

[0055]FIG. 6 shows a predictive method in an inter-field predictivemode;

[0056]FIG. 7 shows the coordinates of a field image;

[0057]FIG. 8 shows the conventional calculation method of a motionvector between corresponding pixels between fields;

[0058]FIG. 9 shows the conventional calculation method of a pixelpointed by a motion vector;

[0059]FIG. 10 shows a conventional method for calculating a chrominancemotion vector, using a luminance motion vector;

[0060]FIG. 11 shows the calculation method of an interpolated pixel of achrominance component;

[0061]FIG. 12 shows the principle of conventional direct mode forexplaining a zero vector between fields with different parity;

[0062]FIG. 13 shows a conventional problem caused if a chrominancemotion vector is calculated using a luminance motion vector when areference field and a coding field are a bottom field and a top field,respectively;

[0063]FIG. 14 shows a conventional problem caused if a chrominancemotion vector is calculated using a luminance motion vector when areference field and a coding field are a top field and a bottom field,respectively;

[0064]FIG. 15 shows the method for generating a chrominance motionvector, using a luminance motion vector in the present invention;

[0065]FIG. 16 shows the operation of one preferred embodiment of thefirst chrominance motion vector generation unit of the presentinvention;

[0066]FIG. 17 shows the operation of one preferred embodiment of thesecond chrominance motion vector generation unit of the presentinvention;

[0067]FIG. 18 is the operation of one preferred embodiment of the thirdchrominance motion vector generation unit of the present invention;

[0068]FIG. 19 is the operation of one preferred embodiment of theselection unit of the present invention;

[0069]FIG. 20 is one example of the present invention which calculates achrominance motion vector using a luminance motion vector when areference field and a coding field are bottom and top fields,respectively; and

[0070]FIG. 21 is one example of the present invention which calculates achrominance motion vector using a luminance motion vector when areference field and a coding field are top and bottom fields,respectively.

[0071]FIG. 22 shows the operation of another preferred embodiment of thefirst chrominance motion vector generation unit of the presentinvention;

[0072]FIG. 23 shows the operation of another preferred embodiment of thesecond chrominance motion vector generation unit of the presentinvention;

[0073]FIG. 24 is the operation of another preferred embodiment of thethird chrominance motion vector generation unit of the presentinvention;

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0074] Firstly, the principle of coding in the present invention isdescribed.

[0075] The motion picture encoding device of the present invention formaking the inter-field motion compensation of a motion picture signalcomposed of a plurality of fields comprises a plurality of chrominancemotion vector generation units generating a chrominance motion vectorusing a luminance motion vector; and a selection unit selecting one ofthe chrominance motion vector generation units used to generate achrominance vector, using the respective parity of the reference fieldand a coding field of a motion vector. The chrominance motion vectorgeneration unit selected by the selection unit generates the chrominancepredictive vector, based on the motion vector information of luminanceinformation.

[0076] If a chrominance motion vector from a coding field to a referencefield is parallel to a luminance motion vector from the coding field tothe reference field, the spatial shift of the luminance motion vectorand that of the chrominance motion vector become the same, that is, therelation of the spatial positions of the luminance motion vector and thechrominance motion vector is preserved, then the color displacementbetween fields disappears.

[0077] Here, the important thing is that, in conventional method, evenif the luminance motion vector is parallel to the chrominance motionvector based on a mathematical expression, each does not become parallelwhen those vectors are mapped on relations between luminance pixels andbetween chrominance pixels which compose each field.

[0078] The plurality of chrominance motion vector generation unitsinclude the three following types.

[0079] A first chrominance motion vector generation unit is selected bythe selection unit when a reference field and a coding field have thesame parity. A second chrominance motion vector generation unit isselected by the selection unit when a reference field and a coding fieldare a top field and a bottom field, respectively. A third chrominancemotion vector generation unit is selected by the selection unit when areference field and a coding field are a bottom field and a top field,respectively.

[0080] A method for calculating a chrominance motion vector parallel toa luminance motion vector depends on the coding field parity andreference field parity of a luminance motion vector. The calculationmethod differs in the following three case: a case where the codingfield parity and reference field parity are the same, a case where thecoding field and reference field are top and bottom fields,respectively, and a case where the coding field and reference field arebottom and top fields, respectively. Therefore, in the presentinvention, an optimal one is selected from the three types ofchrominance motion vector generation units calculating a chrominancemotion vector parallel to a luminance motion vector, depending on thecoding field and the reference field, and a chrominance motion vector isgenerated.

[0081] Specifically, if the reference field parity and coding fieldparity are the same, the first chrominance motion vector generation unitcalculates a chrominance motion vector as follows, assuming that aluminance motion vector indicating the vertical displacement of oneluminance pixel of a field image by the value “1” of the vectorcomponent as units and a chrominance motion vector indicating thevertical displacement of one chrominance pixel of a field image by thevalue “1” of the vector component as units are MVy and MVCy,respectively.

MVCy=Mvy/2  (3)

[0082] If the reference field parity and coding field parity are top andbottom fields, respectively, the second chrominance motion vectorgeneration unit calculates a chrominance motion vector as follows,assuming that a luminance motion vector indicating the verticaldisplacement of one luminance pixel of a field image by the value “1” ofthe vector component as units and a chrominance motion vector indicatingthe vertical displacement of one chrominance pixel of a field image bythe value “1” of the vector component as units are MVy and MVCy,respectively.

MVCy=Mvy/2+0.25  (4)

[0083] If the reference field parity and coding field parity are bottomand top fields, respectively, the third chrominance motion vectorgeneration unit calculates a chrominance motion vector as follows,assuming that a luminance motion vector indicating the verticaldisplacement of one luminance pixel of a field image by the value “1” ofthe vector component as units and a chrominance motion vector indicatingthe vertical displacement of one chrominance pixel of a field image bythe value “1” of the vector component as units are MVy and MVCy,respectively.

MVCy=Mvy/2−0.25  (5)

[0084] Sometimes, the respective units of luminance and chrominancevectors vary, depending on its definition. In the case that it isdefined that a luminance motion vector indicates the displacement of oneluminance moving pixel when the component of the luminance motion vectorchanges by value 4 and that a chrominance motion vector indicates thedisplacement of one chrominance moving pixel when the component of thechrominance motion vector changes by value 8, if the reference fieldparity and coding field parity are the same, the first chrominancemotion vector generation unit calculates a chrominance motion vector asfollows, assuming that a luminance motion vector and a chrominancemotion vector are MVy and MVCy, respectively.

MVCy=Mvy  (6)

[0085] In the same definition, if the parity of reference field andcoding field are top and bottom fields, respectively, the secondchrominance motion vector generation unit calculates a chrominancemotion vector as follows, assuming that a luminance motion vector and achrominance motion vector are MVy and MVCy, respectively.

MVCy=Mvy+2  (7)

[0086] In the same definition, if the reference field parity and codingfield parity are bottom and top fields, respectively, the thirdchrominance motion vector generation unit calculates a chrominancemotion vector as follows, assuming that a luminance motion vector and achrominance motion vector are MVy and MVCy, respectively.

MVCy=Mvy−2  (8)

[0087] The motion picture decoding device of the present inventionbasically has the same functions as the motion picture encoding device,and operates in the same way.

[0088] The preferred embodiments of the encoding device are mainlydescribed below. The encoding device has the configuration describedabove. Since the present invention relates to the vertical component ofa motion vector, it is assumed for convenience sake that the horizontalcomponents of all the motion vectors are 0. In this case, the decodingdevice has the same configuration as the encoding device.

[0089] Preferred embodiments are described below assuming that AVC FCDis adopted.

[0090]FIG. 15 shows a method for calculating a chrominance motion vectorusing a luminance motion vector. The preferred embodiment of a devicegenerating a chrominance motion vector using a luminance motion vectorin a field prediction comprises three types of chrominance motion vectorgeneration units and one selection unit.

[0091] The operation of the present invention shown in FIG. 15 isdescribed below. Firstly it is assumed that a given luminance motionvector 231 is (MV_x,MV_y). This luminance vector is inputted to all of afirst chrominance motion vector generation unit 233, a secondchrominance motion vector generation unit 234 and a third chrominancemotion vector generation unit 235. Then, their respective outputs areinputted to a selection unit 230. The selection unit 230 selects one ofthe respective outputs of the first, second and third chrominance motionvector generation units, based on information about the coding fieldparity 237 of the inputted motion vector and its reference field parity238, and outputs it as a color motion vector 232 (MVC_x, MVC_y).

[0092]FIG. 16 shows the operation of the first chrominance motion vectorgeneration unit. In this preferred embodiment, a luminance motion vector261 (MV_x,MV_y) is inputted to a first chrominance motion vectorgeneration unit 260, and a first chrominance motion vector candidate 262(MVC1_x, MVC1_y) is outputted. The chrominance motion vector generationunit 260 calculates the first chrominance motion vector candidate 262 asfollows using the luminance motion vector 261.

(MVC1_(—) x, MVC1_(—) y)=(MV _(—) x/2, MV _(—) y/2)  (9)

[0093] Then, the calculated first chrominance motion vector candidate262 is outputted to the selection unit.

[0094]FIG. 17 shows the operation of the second chrominance motionvector generation unit. In this preferred embodiment, a luminance motionvector 271 (MV_x,MV_y) is inputted to a second chrominance motion vectorgeneration unit 270, and a second chrominance motion vector candidate272 (MVC2_x, MVC2_y) is outputted. The chrominance motion vectorgeneration unit 270 calculates the second chrominance motion vectorcandidate 272 as follows using the luminance motion vector 271.

(MVC2_(—) x, MVC2_(—) y)=(MV _(—) x/2, MV _(—) y/2+1/4)  (10)

[0095] Then, the calculated second chrominance motion vector candidate272 is outputted to the selection unit.

[0096]FIG. 18 shows the operation of the third chrominance motion vectorgeneration unit. In this preferred embodiment, a luminance motion vector281 (MV_x,MV_y) is inputted to a third chrominance motion vectorgeneration unit 280, and a third chrominance motion vector candidate 282(MVC2_x, MVC2_y) is outputted. The chrominance motion vector generationunit 280 calculates the third chrominance motion vector candidate 282 asfollows using the luminance motion vector 281.

(MVC3_(—) x,MVC3_(—) y)=(MV _(—) x/2,MV _(—) y/2−¼)  (11)

[0097] Then, the calculated third chrominance motion vector candidate282 is outputted to the selection unit.

[0098]FIG. 19 shows the operation of one preferred embodiment of theselection unit 240 of the present invention. Firstly, in this preferredembodiment, a condition judgment table 241 is used for judgment of thecoding field parity 247 of a motion vector and its reference fieldparity 248, and the selection information 249 of a chrominance motionvector generation unit to be selected is outputted. In this preferredembodiment, if the reference field and coding field are the same, thiscondition judgment table 241 is used for outputting selectioninformation indicating the selection of a first chrominance motionvector candidate 244. If reference field and coding field are top andbottom fields, respectively, the condition judgment table 241 is usedfor outputting selection information indicating the selection of asecond chrominance motion vector candidate 245. If reference field andcoding field are bottom and top fields, respectively, the conditionjudgment table 241 is used for outputting selection informationindicating the selection of a third chrominance motion vector 246candidate.

[0099] In this case, the first, second or third chrominance motionvector candidates 244, 245 and 246 are connected to 262 shown in FIG.16, 272 shown in FIG. 17 and 282 shown in FIG. 18, respectively. Then, aselector 243 selects one of the first, second and third chrominancemotion vector candidates 244, 245 and 246, based on the selectioninformation 249, and outputs (MVC_x,MVC_y) as its chrominance motionvector 242.

[0100]FIG. 20 shows the operation of the present invention to calculatea chrominance vector using a luminance vector in the case wherereference field and coding field are bottom and top fields,respectively. In the example shown in FIG. 20, a luminance motion vector(MV_x,MV_y) used to predict a top coding field pixel 160 is assumed tobe (0, 1). In this case, a reference field bottom field luminance pixelposition 161 is selected for the prediction of a luminance pixel 160.The calculation process of a chrominance motion vector to be used topredict a top coding field chrominance pixel 162 is described below withreference to FIG. 15.

[0101] Firstly, in FIG. 20, reference field and coding field are bottomand top fields, respectively. In this case, the condition judgment table241 shown in FIG. 19 is used for selecting selection information 249about the third chrominance motion vector candidate. According toequation (11), the third chrominance motion vector candidate iscalculated as follows. $\begin{matrix}\begin{matrix}{\left( {{MVC3\_ x},{MVC3\_ y}} \right) = \left( {{{MV\_ x}/2},{{{MV\_ y}/2} - {1/4}}} \right)} \\{= \left( {{0/2},{{1/2} - {1/4}}} \right)} \\{= \left( {0,{1/4}} \right)}\end{matrix} & (12)\end{matrix}$

[0102] Then, this value is outputted as the chrominance motion vector242 shown in FIG. 19. If this vector (0,¼) is applied to the top codingfield chrominance pixel 162, a bottom reference field chrominance pixelposition 163 is used as a predicted value. In FIG. 20, the verticalpositional relation between pixels corresponds to a real pixel. As isclear from FIG. 20, a luminance motion vector (0,1) and a chrominancemotion vector (0,¼) are parallel. Thus, the color deviation betweenluminance and chrominance components, which is a conventional problem,can be solved by the present invention.

[0103] Similarly, FIG. 21 shows the operation of the present inventionto calculate a chrominance vector using a luminance vector in the casewhere reference field and coding field are top and bottom fields,respectively.

[0104] In the example shown in FIG. 21, a luminance motion vector(MV_x,MV_y) used to predict a bottom coding field pixel 170 is assumedto be (0,1). In this case, a top reference field luminance pixelposition 171 is selected for the prediction of a luminance pixel 170.The calculation process of a chrominance motion vector to be used topredict a bottom coding field chrominance pixel 172 is described belowwith reference to FIG. 15.

[0105] Firstly, in FIG. 21, reference field and coding field are top andbottom fields, respectively. In this case, the condition judgment table241 shown in FIG. 19 is used for selecting selection information 249about the second chrominance motion vector candidate. According toequation (10), the candidate second chrominance motion vector iscalculated as follows. $\begin{matrix}\begin{matrix}{\left( {{MVC2\_ x},{MVC2\_ y}} \right) = \left( {{{MV\_ x}/2},{{{MV\_ y}/2} + {1/4}}} \right)} \\{= \left( {{0/2},{{1/2} + {1/4}}} \right)} \\{= \left( {0,{3/4}} \right)}\end{matrix} & (13)\end{matrix}$

[0106] Then, this value is outputted as the chrominance motion vector242 shown in FIG. 19. If this vector (0,¾) is applied to the bottomcoding field chrominance pixel 172, a top reference field chrominancepixel position 173 is used as a predictive position. In FIG. 21, thevertical positional relation between pixels corresponds to a real one.As is clear from FIG. 21, a luminance motion vector (0,1) and achrominance motion vector (0,¾) are parallel. Thus, the color deviationbetween luminance and chrominance components, which is a conventionalproblem, can be solved by the present invention.

[0107] Although in the examples shown in FIGS. 20 and 21, the predictionof a specific vector is described, in a prediction between other parityfields, a prediction in which there is no deviation between luminanceand chrominance can also realized by applying this preferred embodiment.

[0108] When the reference field parity and coding field parity are thesame, such color deviation does not occur. Therefore, the result of thefirst chrominance motion vector generation unit 233 of the presentinvention which has the same configuration as a chrominance motionvector generation unit 220 is selected from the conventional luminancemotion vector shown in FIG. 10, and is used as a color motion vector232. Since in this case, a chrominance motion vector calculated by thepresent invention is the same as conventional one, the description ofthis preferred embodiment is omitted here.

[0109] In another aspect of the present invention, equations (9), (10)and (11) vary depending on the units of luminance and chrominance motionvectors.

[0110]FIGS. 22 through 24 show another embodiment of the firstchrominance motion vector generation unit, the second chrominance motionvector generation unit and the third chrominance motion vectorgeneration unit of the present invention.

[0111] In the case that it is defined that a luminance motion vectorindicates the displacement of one luminance moving pixel when the valueof the luminance motion vector changes by four and that a chrominancemotion vector indicates the displacement of one chrominance moving pixelwhen the value of the chrominance motion vector changes by eight, achrominance motion vector generation unit 260 a calculates a candidatefirst chrominance motion vector 262 a using a luminance motion vector261 a as follows.

(MVC1_(—) x,MVC1_(—) y)=(MV _(—) x,MV _(—) y)  (14)

[0112] Then, the calculated first chrominance motion vector candidate262 a is outputted to a selection unit.

[0113] The chrominance motion vector generation unit 270 a calculates asecond chrominance motion vector candidate 272 a using a luminancemotion vector 271 a as follows.

(MVC2_(—) x,MVC2_(—) y)=(MV _(—) x,MV _(—) y+2)  (15)

[0114] Then, the calculated second chrominance motion vector candidate272 a is outputted to a selection unit.

[0115] The chrominance motion vector generation unit 280 a calculates athird chrominance motion vector candidate 282 a using a luminance motionvector 281 a as follows.

(MVC3_(—) x,MVC3_(—) y)=(MV _(—) x,MV _(—) y−2)  (16)

[0116] Then, the calculated third chrominance motion vector candidate282 a is outputted to a selection unit.

[0117] Although this preferred embodiment is described assuming that itadopts AVC FCD, this is just one preferred embodiment, and the formatfor encoding a field image is not limited to this.

[0118] According to the present invention, a chrominance motion vectorparallel to a luminance motion vector can also be calculated in fieldswith different parity, and the deviation in a reference pixel positionbetween luminance and chrominance components, which are the conventionalproblem, can be solved accordingly.

What is claimed is:
 1. A motion picture encoding device for making theinter-field motion compensation of a motion picture signal composed of aplurality of fields, comprising: a plurality of chrominance motionvector generation units generating a chrominance motion vector using aluminance motion vector; and a selection unit selecting one ofchrominance motion vector generation units to be used to generate achrominance vector using reference field parity and encoding fieldparity of a motion vector, wherein a chrominance motion vectorgeneration unit selected by the selection unit generates a predictivechrominance vector, based on motion vector information of luminanceinformation.
 2. The motion picture encoding device according to claim 1,wherein the plurality of said chrominance motion vector generation unitsinclude: a first chrominance motion vector generation unit, which saidselection unit selects when respective parity of a reference field and aencoding field are the same; a second chrominance motion vectorgeneration unit, which said selection unit selects when respectiveparity of a reference field and a encoding field are a top field and abottom field, respectively; and a third chrominance motion vectorgeneration unit, which said selection unit selects when respectiveparity of a reference field and a encoding field are a bottom field anda top field, respectively.
 3. The motion picture encoding deviceaccording to claim 2, wherein said first chrominance motion vectorgeneration unit calculates, assuming that a luminance motion vectorindicating the vertical displacement of one luminance pixel of a fieldimage by a value “1” of a vector component of the luminance motionvector as units and a chrominance motion vector indicating the verticaldisplacement of one chrominance pixel of a field image by a value “1” ofa vector component of the chrominance motion vector as units are MVy andMVCy, respectively, by MVCy=MVy/2.
 4. The motion picture encoding deviceaccording to claim 2, wherein said second chrominance motion vectorgeneration unit calculates, assuming that a luminance motion vectorindicating the vertical displacement of one luminance pixel of a fieldimage by a value “1” of a vector component of the luminance motionvector as units and a chrominance motion vector indicating the verticaldisplacement of one chrominance pixel of a field image by a value “1” ofa vector component of the chrominance motion vector as units are MVy andMVCy, respectively, by MVCy=MVy/2+0.25.
 5. The motion picture encodingdevice according to claim 2, wherein the third chrominance motion vectorgeneration unit calculates, assuming that a luminance motion vectorindicating the vertical displacement of one luminance pixel of a fieldimage by a value “1” of a vector component of the luminance motionvector as units and a chrominance motion vector indicating the verticaldisplacement of one chrominance pixel of a field image by a value “1” ofa vector component of the chrominance motion vector as units are MVy andMVCy, respectively, by MVCy=MVy/2−0.25.
 6. The motion picture encodingdevice according to claim 2, wherein said first chrominance motionvector generation unit calculates, assuming that a luminance motionvector indicating the vertical displacement of one luminance pixel of afield image by a value “4” of a vector component of the luminance motionvector as units and a chrominance motion vector indicating the verticaldisplacement of one chrominance pixel of a field image by a value “8” ofa vector component of the chrominance motion vector as units are MVy andMVCy, respectively, by MVCy=MVy.
 7. The motion picture encoding deviceaccording to claim 2, wherein said second chrominance motion vectorgeneration unit calculates, assuming that a luminance motion vectorindicating the vertical displacement of one luminance pixel of a fieldimage by a value “4” of a vector component of the luminance motionpicture as units and a chrominance motion vector indicating the verticaldisplacement of one chrominance pixel of a field image by a value “8” ofa vector component of the chrominance motion vector as units are MVy andMVCy, respectively, by MVCy=MVy+2.
 8. The motion picture encoding deviceaccording to claim 2, wherein said third chrominance motion vectorgeneration unit calculates, assuming that a luminance motion vectorindicating the vertical displacement of one luminance pixel of a fieldimage by a value “4” of a vector component of the luminance motionvector as units and a chrominance motion vector indicating the verticaldisplacement of one chrominance pixel of a field image by a value “8” ofa vector component of the chrominance motion vector as units are MVy andMVCy, respectively, by MVCy=Mvy−2.
 9. A motion picture decoding devicefor making the inter-field motion compensation of a motion picturesignal composed of a plurality of fields, comprising: a plurality ofchrominance motion vector generation units generating a chrominancemotion vector using a luminance motion vector; and a selection unitselecting one of chrominance motion vector generation units to be usedto generate a chrominance vector using reference field parity anddecoding field parity of a motion vector, wherein a chrominance motionvector generation unit selected by the selection generates a predictivechrominance vector, based on motion vector information of luminanceinformation.
 10. The motion picture decoding device according to claim9, wherein the plurality of said chrominance motion vector generationunits include: a first chrominance motion vector generation unit, whichsaid selection unit selects when respective parity of a reference fieldand a decoding field are the same; a second chrominance motion vectorgeneration unit, which said selection unit selects when respectiveparity of a reference field and a decoding field are a top field and abottom field, respectively; and a third chrominance motion vectorgeneration unit, which said selection unit selects when respectiveparity of a reference field and a decoding field are a bottom field anda top field, respectively.
 11. The motion picture decoding deviceaccording to claim 10, wherein said first chrominance motion vectorgeneration unit calculates, assuming that a luminance motion vectorindicating the vertical displacement of one luminance pixel of a fieldimage by a value “1” of a vector component of the luminance motionvector as units and a chrominance motion vector indicating the verticaldisplacement of one chrominance pixel of a field image by a value “1” ofa vector component of the chrominance motion vector as units are MVy andMVCy, respectively, by MVCy=MVy/2.
 12. The motion picture decodingdevice according to claim 10, wherein said second chrominance motionvector generation unit calculates, assuming that a luminance motionvector indicating the vertical displacement of one luminance pixel of afield image by a value “1” of a vector component of the luminance motionvector as units and a chrominance motion vector indicating the verticaldisplacement of one chrominance pixel of a field image by a value “1” ofa vector component of the chrominance motion vector as units are MVy andMVCy, respectively, by MVCy=MVy/2+0.25.
 13. The motion picture decodingdevice according to claim 10, wherein the third chrominance motionvector generation unit calculates, assuming that a luminance motionvector indicating the vertical displacement of one luminance pixel of afield image by a value “1” of a vector component of the luminance motionvector as units and a chrominance motion vector indicating the verticaldisplacement of one chrominance pixel of a field image by a value “1” ofa vector component of the chrominance motion vector as units are MVy andMVCy, respectively, by MVCy=MVy/2−0.25.
 14. The motion picture decodingdevice according to claim 10, wherein said first chrominance motionvector generation unit calculates, assuming that a luminance motionvector indicating the vertical displacement of one luminance pixel of afield image by a value “4” of a vector component of the luminance motionvector as units and a chrominance motion vector indicating the verticaldisplacement of one chrominance pixel of a field image by a value “8” ofa vector component of the chrominance motion vector as units are MVy andMVCy, respectively, by MVCy=MVy.
 15. The motion picture decoding deviceaccording to claim 10, wherein said second chrominance motion vectorgeneration unit calculates, assuming that a luminance motion vectorindicating the vertical displacement of one luminance pixel of a fieldimage by a value “4” of a vector component of the luminance motionvector as units and a chrominance motion vector indicating the verticaldisplacement of one chrominance pixel of a field image by a value “8” ofa vector component of the chrominance motion vector as units are MVy andMVCy, respectively, by MVCy=MVy+2.
 16. The motion picture decodingdevice according to claim 10, wherein said third chrominance motionvector generation unit calculates, assuming that a luminance motionvector indicating the vertical displacement of one luminance pixel of afield image by a value “4” of a vector component of the luminance motionvector as units and a chrominance motion vector indicating the verticaldisplacement of one chrominance pixel of a field image by a value “8” ofa vector component of the chrominance motion vector as units are MVy andMVCy, respectively, by MVCy=MVy−2.
 17. A program having a computerrealize a motion picture encoding/decoding method for making theinter-field motion compensation of a motion picture signal composed of aplurality of fields, comprising: providing a plurality of chrominancemotion vector generation units generating a chrominance motion vectorusing a luminance motion vector; and selecting one of chrominance motionvector generation units to be used to generate a chrominance vectorusing reference field parity and encoding/decoding field parity of amotion vector, wherein a chrominance motion vector generation unitselected in the selection step generates a predictive chrominancevector, based on motion vector information of luminance information. 18.The program according to claim 17, wherein the plurality of saidchrominance motion vector generation units include: a first chrominancemotion vector generation unit, which said selection unit selects whenrespective parity of a reference field and a encoding/decoding field arethe same; a second chrominance motion vector generation unit, which saidselection unit selects when respective parity of a reference field and aencoding/decoding field are a top field and a bottom field,respectively; and a third chrominance motion vector generation unit,which said selection unit selects when respective parity of a referencefield and a encoding/decoding field are a bottom field and a top field,respectively.
 19. The program according to claim 18, wherein said firstchrominance motion vector generation unit calculates, assuming that aluminance motion vector indicating the vertical displacement of oneluminance pixel of a field image by a value “1” of a vector component ofthe luminance motion vector as units and a chrominance motion vectorindicating the vertical displacement of one chrominance pixel of a fieldimage by a value “1” of a vector component of the chrominance motionvector as units are MVy and MVCy, respectively, by MVCy=MVy/2.
 20. Theprogram according to claim 18, wherein said second chrominance motionvector generation unit calculates, assuming that a luminance motionvector indicating the vertical displacement of one luminance pixel of afield image by a value “1” of a vector component of the luminance motionvector as units and a chrominance motion vector indicating the verticaldisplacement of one chrominance pixel of a field image by a value “1” ofa vector component of the chrominance motion vector as units are MVy andMVCy, respectively, by MVCy=MVy/2+0.25.
 21. The program encoding deviceaccording to claim 18, wherein the third chrominance motion vectorgeneration unit calculates, assuming that a luminance motion vectorindicating the vertical displacement of one luminance pixel of a fieldimage by a value “1” of a vector component of the luminance motionvector as units and a chrominance motion vector indicating the verticaldisplacement of one chrominance pixel of a field image by a value “1” ofa vector component of the chrominance motion vector as units are MVy andMVCy, respectively, by MVCy=Mvy/2−0.25.
 22. The program according toclaim 18, wherein said first chrominance motion vector generation unitcalculates, assuming that a luminance motion vector indicating thevertical displacement of one luminance pixel of a field image by a value“4” of a vector component of the luminance motion vector as units and achrominance motion vector indicating the vertical displacement of onechrominance pixel of a field image by a value “8” of a vector componentof the chrominance motion vector as units are MVy and MVCy,respectively, by MVCy=MVy.
 23. The program according to claim 18,wherein said second chrominance motion vector generation unitcalculates, assuming that a luminance motion vector indicating thevertical displacement of one luminance pixel of a field image by a value“4” of a vector component of the luminance motion picture as units and achrominance motion vector indicating the vertical displacement of onechrominance pixel of a field image by a value “8” of a vector componentof the chrominance motion vector as units are MVy and MVCy,respectively, by MVCy=MVy+2.
 24. The program according to. Claim 18,wherein said third chrominance motion vector generation unit calculates,assuming that a luminance motion vector indicating the verticaldisplacement of one luminance pixel of a field image by a value “4” of avector component of the luminance motion vector as units and achrominance motion vector indicating the vertical displacement of onechrominance pixel of a field image by a value “8” of a vector componentof the chrominance motion vector as units are MVy and MVCy,respectively, by MVCy=Mvy−2.
 25. A motion picture encoding/decodingmethod for making the inter-field motion compensation of a motionpicture signal composed of a plurality of fields, comprising: providinga plurality of chrominance motion vector generation units generating achrominance motion vector using a luminance motion vector; and selectingone of chrominance motion vector generation units to be used to generatea chrominance vector using reference field parity and encoding/decodingfield parity of a motion vector, wherein a chrominance motion vectorgeneration unit selected in the selection step generates a predictivechrominance vector, based on motion vector information of luminanceinformation.
 26. The motion picture encoding/decoding method accordingto claim 25, wherein the plurality of said chrominance motion vectorgeneration units include: a first chrominance motion vector generationunit, which said selection unit selects when respective parity of areference field and a encoding/decoding field are the same; a secondchrominance motion vector generation unit, which said selection unitselects when respective parity of a reference field and aencoding/decoding field are a top field and a bottom field,respectively; and a third chrominance motion vector generation unit,which said selection unit selects when respective parity of a referencefield and a encoding/decoding field are a bottom field and a top field,respectively.